Handbook for Irrigation of Wine Grapes in South Africa
temperature is above 10°C for at least four months. Based on the foregoing, the climate at Stellenbosch is temperate with dry, warm summers, i.e. “Csb” in short. TABLE 1.3. Long term mean monthly air temperature (T n ) and total precipitation (P tot ) recorded at three localities in the Western Cape. Month Stellenbosch Robertson Lutzville T n (°C) P tot (mm) T n (°C) P tot (mm) T n (°C) P tot (mm) January 21.5 21.0 23.2 12.2 22.3 2.1
February
21.8
23.6
23.0
16.4
23.0
3.3
March
20.3
41.6
21.5
15.7
22.0
6.9
April
18.4
62.0
18.4
30.4
20.2
10.5
May
15.9
98.9
15.1
32.5
17.6
17.9
June
13.9
122.3
12.6
31.9
15.5
24.8
July
13.1
103.0
12.0
26.9
14.6
19.6
August
13.5
104.1
12.8
41.8
15.0
19.8
September
14.4
67.4
14.9
19.8
16.3
11.5
October
16.4
40.1
17.5
21.5
18.2
7.7
November
18.7
29.3
20.0
18.4
20.2
6.6
December
20.2
31.0
22.0
12.2
21.3
8.6
Mean
17.3
–
17.8
–
18.9
–
Total
–
744.3
–
279.7
–
139.3
(ii) At Robertson, less than 70% of the annual precipitation occurs in winter. Therefore, the P threshold = (2 x mean annual temperature + 14) = 49.5. Since the mean annual precipitation is less than 495 mm (Table 1.3), it is an arid climate. Given that the mean annual precipitation is more than five times the P threshold , it is regarded as steppe. Furthermore, the temperature is regarded as cold, since the mean annual temperature is less than 18°C (Table 1.3). Therefore, Robertson has an arid, steppe, cold or “BSk” climate. (iii) Since less than 70% of the annual precipitation occurs in winter at Lutzville, the P threshold is 51.7 as calculated from the mean annual temperature. Given that the mean annual precipitation is way below 517 mm (Table 1.3), it is also an arid climate. Since the mean annual precipitation is less than five times the P threshold , it is desert. Furthermore, the locality is regarded as hot, since the mean annual temperature exceeds 18°C (Table 1.3). Therefore, Lutzville has an arid, desert, hot or “BWh” climate.
18 CHAPTER 1 – CLIMATE
Made with FlippingBook - Online catalogs